408 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY. 



757. Bains at sea and their effect upon its equilibrium. — Few 

 persons have ever taken the trouble to compute (§ 402) how 

 much the fall of a single inch of rain over an extensive region in 

 the sea, or how much the change even of two or three degrees of 

 temperature over a few thousand square miles of surface, tends 

 to disturb its equilibrium, and consequently to cause an aqueous 

 palpitation that is felt from the equator to the poles. Let us 

 illustrate by an example : The surface of the Atlantic Ocean 

 covers an area of about twenty-five millions of square miles. 

 Now let us take one fifth of this area, and suppose a fall of rain 

 one inch deep to take place over it. This rain would weigh 

 three hundred and sixty thousand millions of tons ; and the salt 

 which, as water, it held in solution in the sea, and which, when 

 that water was taken up as vapour, was left behind to disturb 

 equilibrium, weighed sixteen millions more of tons, or nearly 

 twice as much as all the ships in the world could carry at a 

 cargo each. This rain might fall in an hour, or it might fall in 

 a day ; but, to occupy what time it might in falling, it is calcu- 

 lated to exert so much force — which is inconceivably great — in 

 disturbing the equilibrium of the ocean. If all the water 

 discharged by the Mississippi Eiver during the year were taken 

 up in one mighty measure and cast into the ocean at one effort, 

 it, would not make a greater disturbance in the equilibrium of 

 the sea, than would the supposed rain-fall. Now this is for but 

 one fifth of the Atlantic, and the area of the Atlantic is about 

 one fifth of the sea area of the world ; and the estimated fall of 

 rain was but one inch, whereas the average for the year is 

 (§ 757) sixty inches ; but we will assume it for the sea to be no 

 more than thirty inches. In the aggregate, and on :an average, 

 then, such a disturbance in the equilibrium of the whole ocean 

 as is here supposed occurs seven hundred and fifty times a year, 



ticularly directed to this feature of the eagre. The term should, j^erhaps, be 

 more comprehensive, and express ' the instantaneous rise and advance of a tidal 

 ■wave ;' the Indian barbarism ' bore ' should be discarded altogether. 



" A very short period elapsed between the passage of the eagre and the re- 

 sumption of traffic. The vessels were soon attached to the shore again ; women 

 and children were occupied in gathering articles which the careless or unskilful 

 had lost in the aquatic melee. The streets were drenched with spray, and a 

 considerable volume of water splashed over the banks into the head of the 

 grand canal, a few feet distant." — Vide Transactions of Chinese Branch of the 

 Moyal Asiatic Society. 



